1. Technical Field
This invention relates to seals within gas turbine engines in general, and to seals for sealing between stator vane segments, in particular.
2. Background Information
Rotor assemblies within most modern gas turbine engines typically include a number of rotor stages separated by stator sections. Each rotor stage generally includes a plurality of blades circumferentially distributed around a disk. Each blade consists of a root, an airfoil, and a platform extending laterally outward between the root and the airfoil. The roots are received within the disk and the platforms collectively form an annular surface at the bases of the airfoils. The stator sections adjacent the rotor sections generally include a plurality of segments that collectively form an annular assembly. Each segment includes one or more vanes extending between an inner and an outer platform. The inner platforms are attached to a static support structure and the outer platforms are supported by the casing disposed radially outside of the stator section. The inner and outer platforms collectively form gas path boundaries through the stator section.
To avoid, or minimize, leakage between stator segments, it is known to provide seals between the inner and outer platforms of adjacent segments. Most inter-segment seals extend axially between segments from forward to aft, and radially along one or both of the forward and aft edges of the segment. Slots machined in circumferential faces (axially and radially extending surfaces) of the segments receive the inter-segment seals.
Inter-segment seals having either a flat plate-like cross-section or a "dog-bone" cross-section are among the most popular. Flat inter-segment seals are often made from sheet metal and may be referred to as "feather seals". The flat geometry offers great flexibility to accommodate misalignment between adjacent stator vane segments. In some instances, however, the flexibility gained by the flat geometry compromises the seals ability to seal between segments.
"Dog-bone" cross-section seals (sometimes referred to as "hour-glass" seals) on the other hand, provide nearly as much flexibility as featherseals and more efficient sealing. A "dog-bone" seal may be described as having a cross-section that includes a pair of substantially u-shaped circumferential ends connected by an arcuate midsection. The u-shaped circumferential ends are received within the slots of adjacent stator vane segments and the arcuate midsection bridges the gap between the adjacent stator vane segments. The convex side of the arcuate midsection extends outwardly toward the higher of the two pressure regions across the seal. The higher pressure deflects the arcuate midsection, consequently biasing the u-shaped circumferential ends within the slots of the stator vane segments. A disadvantage of "dog-bone" type seals is that the cross-sectional geometry precludes a single piece being used for both the axial portion and the radial portion(s) of the stator vane segment seal slot.
What is needed is an apparatus for sealing between stator segments of a gas turbine engine that provides an appropriate amount of flexibility, one that efficiently seals both radially and axially, and one that can be readily manufactured.